1. Field of the Invention
The invention generally relates to electroerosion machines and, more particularly, to wire-cut electric discharge machines which are capable of independent motion in the X and Y axes.
2. Description of Prior Art
In general, electrical discharges between a workpiece and an electrode remove pieces of the workpiece, thereby resulting in the cutting of the workpiece. In wire-cut electric discharge machines, a generally vertically extending wire is used as the electrode. As the wire moves relative to the workpiece, a contour is cut in the workpiece. The operation of machining using wire-cut electroerosion machine may be analogized with the cutting that occurs using a blade in a jigsaw or bandsaw as it cuts a contour in a workpieces.
A conventional EDM machine, such as the one depicted in FIG. 1, has a double deck construction comprising a saddle 4 and a table 6. The saddle 4 moves relative to the fixed bed 2 in the X-axis and the table 6 moves relative to the saddle 4 in the Y-axis. A machining tank 8 is located on the table 6 and holds a machining fluid. A workpiece 12 is mounted within the machining tank 8 by a mounting table 10.
A wire electrode feed mechanism 16 is located on a side of a fixed column 14. The feed mechanism 16 dispenses a wire electrode 18 through an upper guide 20, the workpiece 12, a lower guide 22, to a lower arm 24. The upper guide 20 not only moves in the vertical direction, which is the Z-axis, but also in a U-axis and in a V-axis for performing taper cuts. The lower arm 24 is fixed to the column 14 and to a slide plate. The slide plate enables the machining tank 8 to move in the X-axis relative to the lower arm 24 and provides a liquid tight seal between the lower arm 24 and the machining tank 8. Thus, by moving the saddle 4 in the X-axis and the table 6 in the Y-axis, machining of the workpiece may occur in an X-Y plane. Alternatively, the lower arm may instead be L-shaped and extend down from the fixed column 14 into the machining tank 8 without passing through a side of the tank 8.
The double deck arrangement of the saddle 4 and table 6 is suitable only for small light workpieces. As the workpieces become larger and heavier, the machining tank 8 must expand to accommodate the workpieces. Consequently, the saddle 4 and the table 6 must also be enlarged to maintain a full range of motion within the X-Y plane and so that they can support a heavier load.
The machining area is preferably positioned about 1 meter high to enable easy access by an operator. When larger or heavier workpieces are used, the double deck construction must increase in height in order to be able to withstand the heavier load. With a higher operating area, either a platform is needed to assist the operator to access the machining area or some portions of the machine would have to be embedded. In either event, access to the machining area is hindered.
Additionally, when the workpiece is moved to its furthest position on the Y-axis, forward and rear access to the workpiece is hindered. Thus, it is difficult to insert and remove workpieces from the machining tank 8.
Another example of a conventional EDM machine is illustrated in FIG. 2. The EDM machine depicted in FIG. 2 comprises a table 32 that moves a machining tank 34 along a Y-axis over a pair of rails that are affixed to a fixed bed 30. An upper guide 40 and a lower guide 42 are attached to a moving block 38 through an upper arm and lower arm, respectively. The moving block 38 moves along an X-axis on a pair of guide rails that are affixed to a vertical surface of a column 36. The motion in the X-axis is independent of the motion in the Y-axis.
With the EDM machine of FIG. 2, separate mechanisms are provided for moving the workpiece along the X-axis and the upper and lower guides along the Y-axis. This enables the EDM machine to handle larger and heavier loads without increasing the overall size of the machine.
The EDM machine of FIG. 2, however, still inhibits access to the workpiece when it is moved to its further position in the Y-axis. Also, both ends of the machining tank 34 are blocked by the column 36 to further hinder access to the workpiece. Additionally, an automatic pallet changer for automatically changing the workpieces would be difficult to use with the embodiment of FIG. 2. Further, since the moving block 38 was mounted on its side to the column 36, sub-micron accuracy in the machining is difficult to attain.